No institution within The Oklahoma State System of Higher Education shall enter into a contract for consultant services with any person who has retired from employment with any institution for two (2) years after the retirement date of such person. Nothing in this section shall prohibit an institution within The Oklahoma State System of Higher Education from entering into a contract for a part-time teaching or research position of not more than twelve (12) semester hours per academic year with a person who has retired from employment with an institution within two (2) years after the retirement date of the person; provided that the earnings do not exceed the limitations on earnings pursuant to Section 17-116.10 of this title.